The present invention relates to a pneumatic vehicle tire having a radial carcass and a belt disposed thereabove.
It is customary to provide pneumatic vehicle tires having a radial carcass with a belt that is disposed over the radial carcass and that comprises a number of superimposed belt plies. To increase the elastic force absorption capacity for stresses that occur during operation, the belt plies are built up of parallel steel cords. In this connection, for pneumatic vehicle tires having radial carcasses it is customary to dispose the steel cords of the individual plies in such a way that the steel cords of one ply, when viewed in the circumferential direction, extend at an angle to the equatorial plane of the tire, with the steel cords of the ply disposed thereabove also extending at an angle to the equatorial plane as viewed in the circumferential direction, although extending at an angle in the opposite axial direction of the tire, so that the wire cords of adjacent plies are disposed diagonally and crossed relative to one another. Each of the steel cords is built up in a straightforward manner from a number of individual, twisted together wire filaments. The filaments extend from one side of the tire that delimits the tire in the axial direction, over the equatorial plane, to the other side of the tire that delimits the other axial side of the tire. This known crossing arrangement of the steel cords, including the known radial orientation of the textile filaments of the radial carcass, enables the optimum form of a force absorption triangle for absorbing the forces that act upon the tire during operation.
Due to their formation from a plurality of wire filaments, such steel cords are, on the one hand, dead weight, thus causing an undesirable increase of the rotating dead weight of the tire during operation, and on the other hand also cause problems of fretting due to friction between the filaments disposed in the steel chord. On the other hand, such steel cords very reliably enable the absorption of the forces that act upon the tire during operation. It is therefore desirable to replace the steel cords in the steel belt that are built up in a multi-filament manner, while maintaining their advantageous diagonal and crossing orientation in conventional belts of individual steel cords that extend from one side of the tire to the other, and also while maintaining the reliability of the tire, with individual filaments that are more favorable from a weight standpoint, are more cost effective, and cause no problems with respect to possible fretting phenomena.
Up to now, such wire filaments have not been widely used since although the individual wire filaments have the aforementioned advantages, they can easily break at relatively low compressive and tensile stresses.
EP-OS 0 32 449 discusses the use of wire filaments in the belt of a tire. These wire filaments are oriented parallel to one another in the circumferential direction. In order with such wire filaments that extend parallel to the circumferential direction to also enable the adsorption of force as close as possible to the form of a triangular orientation, the wire filaments that are oriented in the circumferential direction are uniformly waved in the circumferential direction with large wavelengths. Here also there is an increased danger that the individual filaments will break already at relatively low stresses. The identical arrangement of the amplitudes of the individual filaments in the circumferential direction leads to regions that uniformly repeat themselves in the circumferential direction and have particularly poor force absorption capacities, with all of the parallel filaments having an amplitude and to which thus only those forces can be transmitted through the belt that extend in the circumferential direction. This force absorption property that repeats itself at regular intervals in the circumferential direction brings with it an increased danger of filament breakage, as well as an unfavorable oscillation property due to the occurrence of highly harmonic disruptions, which also has a negative impact upon the quietness of rotation of the tire with respect to the generation of noise during operation, and also has a negative impact upon the uniformity of wear.
It is therefore an object of the present invention to provide a pneumatic vehicle tire having a radial carcass and steel belt that enables the advantages of the conventional diagonal and crossing arrangement of the steel cords of the steel belt to be combined with the advantages of the use of individual filaments, while improving the rotational operational characteristics.